Semiconductor devices used in a mobile communication tool such as cellular phone, smartphone, etc. are required to restrain unnecessary electromagnetic waves from leaking to the outside as much as possible, not to exert a negative influence on communication properties. Accordingly, a semiconductor package having an electromagnetic shielding function has been proposed.
For example, electromagnetic shielding of the semiconductor package is performed by covering the surface of a package made of resin with a metal film for electromagnetic shielding, to make this metal film electrically contact with the ground layer of a semiconductor chip in the semiconductor package.
The process of covering the surface of resin with a metal film can be performed by using a sputtering device used in a preceding step in the semiconductor manufacturing process. The sputtering device can simultaneously form uniform metal films for a plurality of semiconductor packages. Therefore, work efficiency can be improved if many semiconductor packages which completed a packaging process are placed on a carrier, conveyed to a sputtering device, and taken into a sputtering vacuum chamber together with the carrier to go through sputtering treatment.
Semiconductor packages which has completed the packaging process but have not yet been electromagnetically shielded are kept in a dedicated tray. One tray stores several tens of semiconductor packages, and thus efficiency of the sputtering treatment can be improved if conveying, to the sputtering device, the carrier having the tray thereon with the semiconductor packages being placed on the tray.
The tray has a plurality of recesses for storing the respective semiconductor packages. The size of the recess is designed in conformity with the size of the semiconductor package, and there is little space between the recess and the semiconductor package. Further, in order to coat not only the top surface of the semiconductor package but also all side surfaces of the semiconductor package with the sputtering metal, the height of each wall between adjacent recesses in the tray is set low. Accordingly, when storing the semiconductor package in each recess of the tray or when conveying the tray storing the semiconductor packages, the semiconductor package may possibly go beyond the recess to ride over the wall. In this case, the semiconductor package is housed while being lifted at an angle. If the sputtering treatment is performed on this inclined semiconductor package by the sputtering device, the sputtering metal adheres also to the bottom surface of the semiconductor package, which may cause electrical short circuit between pads on the bottom surface and the sputtering metal.